# Full text of "Text Book Of Mechanical Engineering"

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```Appendix II.

839

attention to strengths at high temperatures, and he states that
iron and steel usually gain slightly in strength up to 500°, but
after 600° decrease rapidly. For the copper alloys he deduces
the maximum strength:

/ = a - b (t\ - 6o)2

where the values of a and b are as follows :

a.
b.

CoDDer
14. "8
'OOOOI4

Gun-metal (cast)  ...
I 2X
"OOOO5O

Phosphor Bronze (cast)   ... Brass (cast)
A ^ 0
16-1
I 2*£
•OOOO26 "OOOO24

Brass (rolled)        ...........
A*  J 2 A' I
•OOOO28

Delta Metal (rolled)         ......... Muntz Metal (rolled )       .........
31*3
24*7
"OOOO4I "OOOO29

Experiments are made by surrounding the specimen with a
box of oil heated by gas-jets, the measuring apparatus being
outside. (Seej>. 1074.)

EXPERIMENT ON WHITWORTH COMPRESSED STEEL.
BY PROFESSOR GOODMAN.

At 60° Fahr.
At 400° Fahr.

Maximum stress per sq. in. Elastic limit per sq. in __        ... Extension in 10 ins.      ...        ...
34'03 21-97
16%
31-83
20-45
"7%

P. 390. Wohler's Law.—Unwinds formula, p. 390, being
empirical, cannot be proved from first principles, so its application
will be further shewn in the next problem.

Example 62.—Two steel bars, having a static breaking load of 30
tons per square inch, are stressed in tension, the one from 5 to 6 tons
and the other from i to 6 tons per square inch. Find the actual breaking